Exposure time control device for a camera shutter mechanism

ABSTRACT

A camera having a shutter sector movable over and away from a shutter opening is provided with a variably settable holding means to releasably hold the opening is provided with a variably settable holding means to releasably hold the shutter sector in an open position away from the shutter opening for a preselected time duration. The shutter sector is always moved through nearly the same distance to effect an opening of the shutter opening regardless of the exposure time desired. The holding means comprises a lever which is moved into releasable engagement with the shutter sector by the shutter sector itself during its movement to the open position. The lever is moved out of engagement with the shutter sector after a predetermined time period by the action of a biasing spring afterwhich the shutter sector is rapidly moved over the shutter opening. The time duration in which the lever releasably holds the shutter sector in the open position is variable set in accordance with the desired exposure time.

Elnited States Patent Kitai [54] EXPOSURE TIME CONTROL DEVICE FOR ACAMERA SHUTTER MECHANISM [72] Inventor: Kiyoshi Kitai, 54 Tomihisa-cho,Shinjukuku, Tokyo, Japan [22] Filed: April [3, I970 [21 I App]. No.:27,679

[451 July 25, 1972 Primary Examiner-Samuel S. Matthews AssistantExaminer-Monroe H. Hayes Attorney-Robert E. Burns and Emmanuel J. Lobato5 7] ABSTRACT A camera having a shutter sector movable over and awayfrom a shutter opening is provided with a variably settable holdingmeans to releasably hold the opening is provided with a variablysettable holding means to releasably hold the shutter sector in an openposition away from the shutter opening for a preselected time duration.The shutter sector is always moved through nearly the same distance toetfect an opening of the shutter opening regardless of the exposuretime'desired. The holding means comprises a lever which is moved intoreleasable engagement with the shutter sector by the shutter sectoritself during its movement to the open position. The lever is moved outof engagement with the shutter sector after a predetermined time periodby the action of a biasing spring af- 11 Claims, 2 Drawing FiguresEXPOSURE TIME CONTROL DEVICE FOR A CAMERA SHUTTER MECHANISM The presentinvention relates to an exposure time control device for a camerashutter mechanism for use with a camera employing a reciprocatingshutter sector.

The conventional exposure time control devices for reciprocating shuttersectors comprise a shutter sector which is displaced from a closedposition to a variable open position which is determined in accordancewith the particular exposure time desired. If a relatively shortexposure time is needed, the shutter sector is just barely moved awayfrom the shutter opening whereas if a large exposure time is desired,the shutter sector is swung or reciprocated a substantial distance fromthe shutter opening. In other words, the prior art mechanisms employ amovable shutter which is displaced by an amount corresponding to theparticular exposure time desired. If a long exposure time is needed, theshutter is displaced a predetermined distance away from the shutteropening such that the time that it takes for the shutter to move backinto position where it completely covers the shutter opening correspondsto the desired exposure time. If a short exposure time is desired, theshutter sector is pivoted away from the shutter opening by a very smalldistance and then allowed to swing back over the shutter opening suchthat the desired exposure time corresponds to the time that it takes forthe shutter sector to swing through its variably set opening distanceand back to its closed position.

The major drawback of the above-mentioned exposure time control devicesare that the length of the exposure time is directly related to theamplitude of displacement of the shutter sector. Hence, space necessaryto accommodate the reciprocating action of the shutter sector increasesas the exposure time is increased. Cameras employing the above-mentionedtype of exposure time control device have a very definite and fixedratio of exposure time ranges to actual size of the camera. Such camerasusually have a short exposure time of about l/90 of a second and a longexposure time of about 1/40 of a second.

It is accordingly a principal object of the present invention to providean exposure control device for a camera shutter mechanism wherein theexposure time is not related to the amplitude of displacement of thesector.

It is another object of the present invention to provide an exposurecontrol device for a camera shutter mechanism wherein the controllableratio of short exposure time to long exposure time can be greatlyincreased.

According to the present invention, a shutter sector cooperates with avariably settable holding means which holds the shutter in its openposition for a predetermined exposure time period. The variably settableholding means is variably set in accordance with the desired exposuretime. The shutter sector is spring biased towards its closed positionand is opened by means of a manually actuated release lever cooperatingwith a spring biased driving lever. The variably settable holding meanscomprises a pivotally mounted control lever which releasably engageswith the shutter sector when same is in its open position and disengageswith the shutter sector after a variably set time period correspondingto the desired exposure time.

Other features and advantages of the exposure control device inaccordance with the present invention will be better understood asdescribed in the following specification and appended claims, when takenin conjunction with the following drawings in which:

FIG. 1 is a perspective view of a camera shutter mechanism embodying theexposure time control device of the present invention showing theshutter in its closed position and the various mechanisms in theircharged or cocked condition; and

FIG. 2 shows the camera shutter mechanism of FIG. 1 but in a differentexposure time setting and wherein the shutter is in its open position.

A preferred embodiment of the present invention will now be explained indetail in conjunction with FIGS. 1 and 2. FIG. I depicts a camerashutter mechanism in its charged or cocked condition. A base plate 1 isprovided with a shutter opening la. A shaft or pin 2 is mounted on thebase plate 1 and receives therearound a biasing spring 3. In addition, asector lever 4 is mounted for rotation on the pin 2 and is continuallybiased in a clockwise direction by the biasing spring 3 cooperating witha pair of pins 6, 6. A shutter sector 5 is connected to the sector orblade lever 4 and functions to-open and close the shutter opening 1a inresponse to pivotal movement of the sector lever 4 about the pin 2. Thepin 6 is connected to the base plate 1 and also functions as a stop orlimit pin effec tive to limit the clockwise movement of the sector 5 toa suitable position wherein it completely closes the shutter opening 1A.

A driving lever 7 is rotatably mounted on a shaft 8 which is fixed tothe base plate 1. A biasing spring 9 is provided for continually biasingthe driving lever in a clockwise direction about the shafi 8. Thedriving lever 7 is provided with an arm 7a which releasably engages witha release lever as hereinafter discussed.

Another pin 10 is fixed to the base plate 1 and a release lever 12 isrotatably mounted on the pin 10. A biasing spring 11 cooperates with apair of stops 25, 25 to continually bias the release lever 12 in acounterclockwise direction about the pin 10. The release lever includesa projection 12a which releasably engages with the arm 7a of the drivinglever 7.

A change-over mechanism is mounted on the driving lever 7 and permitsthe driving lever 7 to be recocked. The changeover mechanism comprises apin 13 secured to the driving lever 7 and a change-over lever 15rotatably mounted on the pin 13. A biasing spring 14 surrounds the pin13 and cooperates with a pair of pins 16, 16' to continually urge thechange-over lever in a counterclockwise direction around the pin 13. Thechange-over lever 15 is provided with a camming portion 15a which coactswith a camming surface 4a of the sector lever 4 to effect pivotalmovement of the sector lever 4 in a counterclockwise direction inresponse to clockwise movement of the driving lever 7.

When the release lever 12 is manually actuated, the projection 12adisengages from the arm 70 of the driving lever thereby pemiitting thebiasing spring 9 to rotate the driving lever 7 in a clockwise directionwhereby the sector lever 4 along with the sector 5 is cammed intocounterclockwise rotation about the pin 2, thus opening the shutter.When the shutter mechanism is recocked, the change-over lever 15 comesinto contact with the bottom portion of the sector lever 4 and isthereby pivoted against the force of the spring 14 about the pin 13 toallow the driving lever 7 to move past the sector lever 4.

A control lever 19 is rotatably mounted on a pin 17 which is affixed tothe base plate 1. A biasing spring 18 cooperates with a pair of pins 20,20' to constantly bias the control lever 19 in a counterclockwisedirection around the pin 17. The control lever 19 is provided with acamming projection 19a which coacts with a camming surface 4b of thesector lever 4 and another camming projection 19!: which coacts with theaforementioned camming surface 4a of the sector lever 4. The controllever 19 is also provided with a slot which connects the control lever19 to a speed-regulating device.

A flywheel 22 is rotatably mounted on a pin 21 which is attached to thebase plate 1. The flywheel 22 is provided with a plurality of step-likeprojections 22A, 22b, 22c which cooperate with the speed-regulatingdevice. A pin 22d is connected to the flywheel 22 and rides in the slot190 provided in the control lever 19 thereby providing the drivingconnection between the control lever 19 and the flywheel 22. Aconventional speed-regulating device is connected to the base plate 1and comprises a speed-regulating lever 24 having an end portion 240which releasably engages with respective ones of the step-likeprojections 22a, 22b, 22c. The speed-regulating lever 24 is connected toa shaft 23 which is rotationally driven and preset in any desiredposition by an exposure meter, by hand, or by any other well knownmethod. The step-like projection 22a corresponds to the most rapidexposure time whereas the projection 22c corresponds to the slowestexposure time, as more fully described below.

The operation of the present invention will now be explained. FIG. 1shows the shutter sector 5 in its closed position and shows the variousmechanisms in their charged or cocked positions. In FIG. 1, the endportion 24a of the speed-regulating lever 24 is preset to the positioncorresponding to the shortest exposure time and in such a position, thelever 24 is in releasable engagement with the projection 22a on theflywheel 22. With such a setting, the shutter sector 5 is set for itsmost rapid closing speed. When the release lever 12 is manually actuatedto effect disengagement of the driving lever 7, the driving lever 7rotates in a clockwise direction due to the force of the biasing spring9 and the camming portion a of the change-over lever 15 comes in cammingcontact with the camming surface 4a and effects a counterclockwisemovement of the sector lever 4, thereby opening the shutter opening 1A.The driving lever 7 continues to rotate in a clockwise direction untilthe arm 7a abuts against the stop pin 25 and during this rotation, thecamming portion 15a moves out of contact with the cam surface 4A. As thesector lever 4 is pivoted in a counterclockwise direction against theaction of the spring 3, the sector 5 is accordingly moved away from theshutter opening 1A. The sector 5 and the sector lever 4 are sodimensioned that when the sector 5 is completely away from the shutteropening 1A, the camming surface 4b strikes against the projection 19a ofthe control lever 19. The abutment of the sector lever 4 with thecontrol lever 19 tends to rotate the control lever 19 in a clockwisedirection, but such movement is prevented since the lever 24 is inengagement with the projection 22a of the flywheel and since theflywheel 22 is thus locked against counterclockwise rotation, thecontrol lever 19 is prevented from undergoing clockwise rotation. Thesector lever 4 is then rapidly driven in a clockwise direction by thecompressive force stored in the spring 3 and the sector 5 rapidly closesover the shutter opening 1.4. With such a setting of thespeed-regulating lever 24, the sector 5 is rapidly moved through itsshutter opening-and-closing cycle and such corresponds to the shortestexposure time.

FIG. 2 depicts the shutter mechanism in the open position and also showsthe operation of the device when the speedregulating lever 24 is set toengage with the step-like projection 22c corresponding to the longestexposure time. Again, the speed-regulating lever 24 is preset in aposition corresponding to the desired exposure time and the variouselements assume the position shown in FIG. 1 with the exception that thespeed-regulating lever 24 occupies the position shown in FIG. 2. Whenthe release lever 12 is manually depressed, the driving lever 7 rotatesclockwise and the cam portion 15a of the change-over lever 15 comes intocontact with and pivots the sector lever 4 in a counterclockwisedirection around the pin 2 thereby opening the shutter opening 1A. Asthe sector lever 4 rotates in a counterclockwise direction, the cammingsurface 4b comes into contact with the camming projection 19a of thecontrol lever 19 and pivots the control lever 19 in a clockwisedirection about the pin 17.

It should be noted that with this setting of the speed-regulating lever24, the flywheel 22 is free to rotate in a counterclockwise directionuntil the stop-like projection 22c engages with the end portion 24a ofthe speed-regulating lever. Thus, the motion of the driving lever 7 istransmitted through the sector lever 4 to effect a rotational movementof the control lever 19 and hence, a corresponding counterclockwiserotation of the flywheel 22. As the control lever 19 is driven in aclockwise direction, the biasing spring 18 is further compressed and theprojection 19b is pivoted around the camming surface AM, as shown inFIG. 2.

As the flywheel 22 rotates in a counterclockwise direction, the steplikeprojection 22c comes into engagement with the speed-regulating lever 24thereby terminating the motion of the control lever 19 and the flywheel22. As discussed above with reference to FIG. 1, the biasing spring 3constantly tends to pivot the sector lever 4 in a clockwise direction toeffect closing of the shutter opening 1a, but in this instance, theprojection 19b releasably engages with the camming surface 4a therebytemporarily preventing the biasing spring 3 from closing the shuttersector 5. This temporary holding of the shutter sector in the openposition exists for a predetermined time duration depending upon thevariable setting selected for the speed-regulating lever 24. Meanwhile,the biasing spring 18 pivots the control lever 19 in a counterclockwisedirection allowing the projection 19b to slide along the camming surface4a until the engagement between these two members is terminated. As soonas the control member 19 disengages from the sector lever 4, the biasingspring 3 rapidly pivots the sector lever 4 along with the sector 5 in aclockwise direction effecting a closing of the shutter opening 1A.

It can thus be seen that the function of the control lever 19 is tocontrol the exposure time of the shutter la by delaying the closing ofthe shutter sector 5 for a predetermined time period corresponding tothe time interval selected by the speed-regulating lever 24. Thespeed-regulating lever 24, the flywheel 22 and the control lever 19comprise a variably settable holding means which is operative toreleasably hold the shutter sector in its open position for a variableand preselected time duration. In a similar manner, the speedregulatinglever 24 could be preset to engage with the step-like timing projection22b and this would result in the projection 19b engaging with a smallersurface area of the camming surface 4a and hence result in a shorterexposure time. The control lever 19 is thus sequentially moved from itsinitial position by the camming action of the shutter to one of aplurality of dilferent preselected holding positions (one of which isshown in FIG. 2) and then back to its initial position by the biasingforce of the spring 18 to releasably hold the shutter in the openposition for a time period determined by one of the holding positions.Any number of step-like timing projections 22a, 22b, 22c can be employedand it should be noted that the varying angular distance through whichthe flywheel 22 rotates determines the exposure time of the shuttermechanism. Alternatively, the flywheel 22 could be eliminated andstep-like projections could be provided on the control lever 19cooperating directly with the speed-regulating lever 24.

According to the present invention, the exposure time of a shuttermechanism can be variably set in a relatively simple manner. Theoperation of the control lever 19 permits the manufacturing of a camerahaving a much larger ratio of short exposure time to long exposure timewithout unduly increasing the size of the camera.

What I claim and desire to secure by Letters Patent is:

l. An exposure control device for a camera shutter mechanism comprising:a movably mounted shutter cyclically movable from a normally closedposition to an open position and back to said closed position definingan exposure time; biasing means constantly biasing said shutter to saidclosed position; drive means for driving said shutter from said closedposition to said open position and variably settable holding meanssequentially movable from an initial position by said shutter duringopening movement thereof to one of a plurality of different preselectedholding positions each corresponding to a diiferent preselected exposuretime and then back to said initial position for releasably holding saidshutter in said open position for a time period variably set inaccordance with one of said preselected exposure times.

2. An exposure control device according to claim 1, wherein saidvariably settable holding means comprises a rotatably mounted controllever actuated during movement of said shutter to said open position toreleasably hold said shutter in said open position; and means connectedto said control lever for variably setting the time duration saidcontrol lever holds said shutter in said open position.

3. An exposure control device according to claim 2, wherein saidlast-mentioned means comprises a rotatably mounted member having aplurality of timing projections thereon each corresponding to apredetermined exposure time, a pivotally mounted regulating leverpivotal to a plurality of positions to effect releasable engagement withone of said projections during rotation of said member, and meansconnecting said control lever to said member to effect rotation of saidmember in response to rotational movement of said control lever.

4. An exposure control device according to claim 3, wherein said shutterincludes two camming surfaces; said control lever includes a firstprojection releasably engageable with one of said camming surfacesduring movement of said shutter to said open position to effectrotational movement of said control lever in one direction and a secondprojection releasably engageable with the other of said camming surfaceswhen said shutter is in said open position; and biasing means forcontinually biasing said control lever in a direction opposite to saidone direction.

5. An exposure control device according to claim 4, wherein said drivemeans comprises a rotatably mounted driving lever rotatable in a drivingdirection to drive said shutter from said normally closed position tosaid open position; means for continually urging said driving lever insaid driving direction; and a manually operable release levercooperative with said driving lever to effect opening of said shutter.

6. An exposure control device according to claim 2, wherein said shutterincludes two camming surfaces, and wherein said control lever includes afirst projection releasably engageable with one of said camming surfacesduring movement of said shutter to said open position to effectrotational movement of said control lever in one direction and a secondprojection releasably engageable with the other of said camming surfaceswhen said shutter is in said open position; and biasing means forcontinually biasing said control lever in a direction opposite to saidone direction.

7. An exposure control device according to claim 6, wherein said drivemeans comprises a rotatably mounted driving lever rotatable in a drivingdirection to drive said shutter from said normally closed position tosaid open position; means for continually urging said driving lever insaid-driving direction; and a manually operable release levercooperative with said driving lever to efl'ect opening of said shutter.

8. An exposure control device according to claim 1, wherein said holdingmeans comprises a movable control lever, means mounting said controllever for movement to said initial and holding positions, spring meanscontinually biasing said control lever to said initial position, firstmeans on said control lever engageable with said shutter to effectmovement of said control lever from said initial position to one of saidholding positions in response to opening movement of said shutter,second means on said control lever engageable with said shutter forreleasably holding said shutter in said open position for a time perioddetermined by the particular holding position of said control lever, andmeans for variably setting the desired holding position of said controllever in accordance with one of said preselected exposure times.

9. An exposure control device for a camera shutter mechanism comprising:a movably mounted shutter blade cyclically movable along a path from anormally closed position to an open position and back to said closedposition defining an exposure time; biasing means constantly biasingsaid shutter blade to said closed position; drive means for driving saidshutter blade from said closed position to said open position; andholding means biased towards an initial position and having a firstprojection projecting into the opening path of said shutter blade suchthat said holding means is displaced from said initial position by saidshutter blade during movement of said shutter blade to said openposition, said holding means having a second projection projecting intosaid shutter blade path behind said shutter blade when said holdingmeans is displaced from its initial position for holding said shutterblade in said open position while said holding means is displaced fromits initial position and releasing said shutter blade when said holdingmeans returns to its initial position by its own biasing.

10. An exposure control device according to claim 9, wherein. saidholding means comprises a rotatably mounted control lever actuatedduring movement of said shutter blade to said open position toreleasably hold said shutter blade, a rotatably mounted member having aplurality of timing projections thereof each corresponding to apredetermined exposure time, a pivotally mounted regulating leverpivotal to a plurality of positions to effect releasable engagement withone of said projections during rotation of said member, and meansconnecting said control lever to said member to effect rotation of saidmember in response to rotational movement of said control lever.

11. An exposure control device according to claim 9, wherein saidshutter blade includes two camming surfaces; and wherein said holdingmeans comprises a rotatably mounted control lever including a firstprojection releasably engageable with one of said camming surfacesduring movement of said shutter blade to said open position to effectrotational movement of said control lever in one direction and a secondprojection releasably engageable with the other of said camming surfaceswhen said shutter blade is in said open position; and biasing means forcontinually biasing said control lever in a direction opposite to saidone direction.

1. An exposure control device for a camera shutter mechanism comprising:a movably mounted shutter cyclically movable from a normally closedposition to an open position and back to said closed position definingan exposure time; biasing means constantly biasing said shutter to saidclosed position; drive means for driving said shutter from said closedposition to said open position and variably settable holding meanssequentially movable from an initial position by said shutter duringopening movement thereof to one of a plurality of different preselectedholding positions each corresponding to a different preselected exposuretime and then back to said initial position for releasably holding saidshutter in said open position for a time period variably set inaccordance with one of said preselected exposure times.
 2. An exposurecontrol device according to claim 1, wherein said variably settableholding means comprises a rotatably mounted control lever actuatedduring movement of said shutter to said open position to releasably holdsaid shutter in said open position; and means connected to said controllever for variably setting the time duration said control lever holdssaid shutter in said open position.
 3. An exposure control deviceaccording to claim 2, wherein said last-mentioned means comprises arotatably mounted member having a plurality of timing projectionsthereon each corresponding to a predetermined exposure time, a pivotallymounted regulating lever pivotal to a plurality of positions to effectreleasable engagement with one of said projections during rotation ofsaid member, and means connecting said control lever to said member toeffect rotation of said member in response to rotational movement ofsaid control lever.
 4. An exposure control device according to claim 3,wherein said shutter includes two camming surfaces; said control leverincludes a first projection releasably engageable with one of saidcamming surfaces during movement of said shutter to said open positionto effect rotational movement of said control lever in one direction anda second projection releasably engageable with the other of said cammingsurfaces when said shutter is in said open position; and biasing meansfor continually biasing said control lever in a direction opposite tosaid one direction.
 5. An exposure control device according to claim 4,wherein said drive means comprises a rotatably mounted driving leverrotatable in a driving direction to drive said shutter from saidnormally closed position to said open position; means for continuallyurging said driving lever iN said driving direction; and a manuallyoperable release lever cooperative with said driving lever to effectopening of said shutter.
 6. An exposure control device according toclaim 2, wherein said shutter includes two camming surfaces, and whereinsaid control lever includes a first projection releasably engageablewith one of said camming surfaces during movement of said shutter tosaid open position to effect rotational movement of said control leverin one direction and a second projection releasably engageable with theother of said camming surfaces when said shutter is in said openposition; and biasing means for continually biasing said control leverin a direction opposite to said one direction.
 7. An exposure controldevice according to claim 6, wherein said drive means comprises arotatably mounted driving lever rotatable in a driving direction todrive said shutter from said normally closed position to said openposition; means for continually urging said driving lever in saiddriving direction; and a manually operable release lever cooperativewith said driving lever to effect opening of said shutter.
 8. Anexposure control device according to claim 1, wherein said holding meanscomprises a movable control lever, means mounting said control lever formovement to said initial and holding positions, spring means continuallybiasing said control lever to said initial position, first means on saidcontrol lever engageable with said shutter to effect movement of saidcontrol lever from said initial position to one of said holdingpositions in response to opening movement of said shutter, second meanson said control lever engageable with said shutter for releasablyholding said shutter in said open position for a time period determinedby the particular holding position of said control lever, and means forvariably setting the desired holding position of said control lever inaccordance with one of said preselected exposure times.
 9. An exposurecontrol device for a camera shutter mechanism comprising: a movablymounted shutter blade cyclically movable along a path from a normallyclosed position to an open position and back to said closed positiondefining an exposure time; biasing means constantly biasing said shutterblade to said closed position; drive means for driving said shutterblade from said closed position to said open position; and holding meansbiased towards an initial position and having a first projectionprojecting into the opening path of said shutter blade such that saidholding means is displaced from said initial position by said shutterblade during movement of said shutter blade to said open position, saidholding means having a second projection projecting into said shutterblade path behind said shutter blade when said holding means isdisplaced from its initial position for holding said shutter blade insaid open position while said holding means is displaced from itsinitial position and releasing said shutter blade when said holdingmeans returns to its initial position by its own biasing.
 10. Anexposure control device according to claim 9, wherein said holding meanscomprises a rotatably mounted control lever actuated during movement ofsaid shutter blade to said open position to releasably hold said shutterblade, a rotatably mounted member having a plurality of timingprojections thereof each corresponding to a predetermined exposure time,a pivotally mounted regulating lever pivotal to a plurality of positionsto effect releasable engagement with one of said projections duringrotation of said member, and means connecting said control lever to saidmember to effect rotation of said member in response to rotationalmovement of said control lever.
 11. An exposure control device accordingto claim 9, wherein said shutter blade includes two camming surfaces;and wherein said holding means comprises a rotatably mounted controllever including a first projection releasably engageable with one ofsaid camming surfaces during movement Of said shutter blade to said openposition to effect rotational movement of said control lever in onedirection and a second projection releasably engageable with the otherof said camming surfaces when said shutter blade is in said openposition; and biasing means for continually biasing said control leverin a direction opposite to said one direction.